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5245 > gram positive lecture > Flashcards

gram positive lecture Flashcards

1
Q

what is the most common organism on the surface of the skin?

A

staph epidermidis

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2
Q

compare staph aureus and epidermidis with regards to:

  • protein A
  • coagulase
  • catalase
  • hyaluronidase
  • staphylokinase
  • lipase
  • beta lactamase
A

staph aureus is positive for all of the categories

staph epidermidis is positive in catalase and lipase, and negative in the rest

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3
Q

what are the 3 areas of pathogenicity of staph aureus?

A
  1. structures that enable staph to evade phagocytosis
  2. production of enzymes
  3. production of toxins
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4
Q

what are the 3 categories of staphylococcal disease?

A

noninvasive
- food poisoning

cutaneous
- various skin conditions

systemic disease

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5
Q

what are the structural defenses of staph aureus (3)

A
  1. protein A coats the bacterial surface
  2. bound coagulase
  3. enzymes
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6
Q

describe how protein A is a structural defense for staph aureus

A

protein A costs the bacterial surface

  • this interferes with humoral immune responses by binding IgG antibodies at the Fc end
  • this inhibits opsonization
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7
Q

describe how bound coagulase is a structural defense in staph aureus

A

converts the soluble blood protein fibrinogen into insoluble fibrin molecules that form blood clots
- fibrin clots hide the bacteria from phagocytosis

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8
Q

which enzymes are involved in structural defense for staph aureus, and describe each

A
  • cell free coagulase
  • hyaluronidase
  • staphylokinase
  • lipases
  • beta lactamase
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9
Q

describe the function of cell free coagulase and staphylokinase

A

cell free coagulase
- triggers fibrin formation

staphylokinase

  • dissolves fibrin threads in blood clots
  • allows s. aureus to free itself from clots
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10
Q

describe cytolytic toxins

A
  • alpha toxins are pore forming toxins

- PVL are beta pore forming toxins that can lyse leukocytes

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11
Q

describe enterotoxins

A

stimulate the intestinal muscle contractions, nausea, and intense vomiting

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12
Q

what diseases are caused by staphylococcus?

A
  • food poisoning
  • colitis
  • impetigo
  • furuncle/carbuncle (boil)
  • scalded skin syndrome
  • systemic diseases
    • TSS, bacteremia, endocarditis, pneumonia, osteomyelitis
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13
Q

what drgs are used to treat staph diseases

A

methicillins

  • vancomycin for MRSA
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14
Q

what is the most important measure in preventing nosocomial infections

A

hand antiseptis

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15
Q

describe the lancefield classification

A

divides streptococci into serotypes based on the bacteria’s C antigens

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16
Q

how does GAS cause disease

A
  • depletes normal microbiota
  • large inoculum enable the straptococci to establish themselves before antibodies are formed against them
  • specific immunity is impaired
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17
Q

describe the pathogenicity of strep pyogenes

A

structural components
- protein M interferes with opsonization and lysis of bacteria to camouflages the bacteria

enzymes
- various enzymes spread through tissues

pyrogenic toxins stimulate macrophages and helper T cells to release cytokines

streptolysins lyse red blood cells, white blood cells and platelets

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18
Q

what diseases are caused by GAS?

A
  • pharyngitis (strep throat)
  • scarlet fever
  • pyoderma
  • erysipelas
  • streptococcal TSS
  • necrotizing fasciitis (flesh eating strep)
  • poststreptococcal sequelae (rheumatic fever and glomerulonephritis)
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19
Q

what is the treatment for GAS?

A

penicillin G

20
Q

what is significant about alpha-hemolytic streptococci in dentistry?

A

it plays a major role in dental caries and plaque production

21
Q

what bacteria was the leading cause of death before antibiotics?

A

strep pneumoniae

22
Q

describe the mechanism of strep pneumoniae

A

plysaccharide capsule binds factor H to inhibit the alternative pathway complement and also protects the bacteria from phagocytosis

23
Q

what diseases are associated with strep pneumoniae

A
  • pneumococcal pneumoniae
  • sinusitis and otitis medis
  • bacteremia and endocarditis
  • pneumococcal meningitis
24
Q

what is the treatment for strep pneumoniae

A

penicillin or cephalosporins

25
Q

describe enterococcus

  • conditions it can grow
  • where its found, where it can be harmful
  • resistance to
A

conditions
- 45 degrees C, ph of 9.6, in 6.5% NaCl, 40% bile

where its found
- human colon, not harmful here

where its harmful
- if it spresds to lungs, urinary tract or bloodstream

resistant to

  • most beta lactams, sulfonamides, aminoglycosides
  • often resistant to tetracyclines and erythromycin
  • some strains resistant to cancomycin = VRE
26
Q

what diseases are associated with bacillus anthracis

A
  • anthrax
  • B. cereus
    • responsible for food poisoning in cooked fods
  • B. subtilis
    • produces bacitracin
27
Q

how do humans contract bacillus anthracis

A
  • inhalation of spores
  • inoculation of spores ito the body through a break in the skin
  • ingestion of spores
28
Q

what plasmids are the virulence factors for anthrax encoded?

A

px01 and px02

29
Q

describe the 3 forms anthrax can take form in humans

A
  • inhalation
    • also called woolsorters disease
  • gastrointestinal
    • from ingestion of spore contaminated meats
  • cutaneous
    • marked by eschar (black, necrotic) skin lesions
30
Q

what treatment is used for B. anthracis

A

ciproflaxacin

31
Q

what diseases are caused by clostridium perfringens

A
  • food poisoning
  • gas gangrene
  • myonecrosis
32
Q

describe the toxins in gas gangrene

A

alpha: lecithinase

theta:
- pore forming toxin that alters capillary permeability
- toxic to heart and kidneys
- closely related to SLO

33
Q

what diseases are associated with clostridium difficile

A
  • explosive diarrhea
  • pseudomembranous colitis
    • this can result in perforation of the colon, leading to massive internal infection by fecal bacteria and eventual death
34
Q

what are the 3 forms of botulism

A

food born

  • comes from consumption of toxin in home caned foods or preserved fish
  • can result in progressive paralysis

infant
- results from ingestion of endospores which will germinate and colonize the GI tract due to lack of normal microbiota

wound
- wound becomes contaminated with endospores

35
Q

what diseases are associated with clostridium tetani

A

tetanus (lockjaw, spastic paralysis)

36
Q

what does c. tetani block that leads to paralysis?

A

glycine release, which will inhibit muscle contraction

37
Q

where is listeria monocytogenes found?

A

soil, water, mammals, birds, fish and insects

38
Q

describe the toxins and enzymes produced by listeria monocytogenes

A

l. monocytogenes does not produce any toxins or enzymes

39
Q

how does l. monocytogenes avoid the immune system?

A

internalin
- invasion associated surface protein

listeriolysin O
- pore forming cytotoxin used for escape

40
Q

what is l. monocytogenes resisnt to?

A

heat
cold
salt
ph extremes

41
Q

who is highly susceptible to mild forms of l. monocytogenes?

A

pregnant women

42
Q

how is l. monocytogenes treated?

A

ampicillin

43
Q

bull neck is a sympton of what

A

diphtheria

44
Q

how is diphtheria treated

A

antitoxin, then penicillin or erythromycin

45
Q

what bacteria is detected using the schick test

A

corynebacterium diptheriae

46
Q

what is the significance of actinomyces species as it relates to dentistry

A

major component of dental plaque that increaes gingivitis, also associated with root caries

47
Q

what is used to treat actinomyces

A

amoxicillin

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